7 Appendix E: Quirks Mode Emulation

In Windows Internet Explorer 9, when a document is displayed in IE9 Mode, the browser loads a different rendering engine than that it used in Windows Internet Explorer 8 and Windows Internet Explorer 7. Although the newer rendering engine is only used when Windows Internet Explorer detects that an HTML page has requested the highest level of support for standards, the same is not always true for child pages that might be loaded within frame and iframe elements. Because only one rendering engine can be active at a time, IE9 Mode also includes emulation for Quirks Mode.